Electrical contact device



March A 'H. FoRRER 2,876,336 ELECTRICAL CbNTAcf DEVICE Filed Aug. 26. 1958 2 Sheets-Sheet 1 Hans Ferrer March 3, 1959 Filed Aug. 26, 1958 H. FORRER ELECTRICL CONTACT DEVICE 2 Sheets-Sheet 2 United States Patent O ELECTRICAL CONTACT DEVICE Hans Forrer, Neuenhof, Switzerland, assignor to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a company of Switzerland Application August 26, 1958, Serial No. 757,409

Claims priority, application Switzerland September 6, 1957 Claims. (Cl. 219-156) The present invention relates to an electrical contact device and more particularly to such a device for contacting the end of a steel bar which is to be heated electrically for the purpose of annealing the same. One such contact device is applied to each end of the bar and current is sent longitudinally through the same thus resulting in the bar being heated by the well-known resistance method.

Billets, plate slabs and other elongated steel bar elements have been heated in this manner but considerable diiculty has been experienced in establishing a satisfactory electrical contact at the bar end in any simple manner. It has been proposed in the past to bring the bar to be heated into engagement with contact members both at the sides and end of the bar and wherein the contacts are actuated by means of a hydraulic system with an operating cylinder for each contact member in order to clamp and release the bar from the contact member. Such contact devices are relatively complicated, however, and involve considerably high cost. Moreover, they do not ensure suicient safety for making the contact during the heating operation, since the contact pressure against the bar drops immediately whenever any trouble occurs in the hydraulic control system, thus leading possibly to the formation of arcs at the contacts and even tires.

The object of the present invention is to provide an improved contact structure which avoids the disadvantages of the prior known constructions. The improved construction features at least two side contact members and also an end contact member, if desired, for each end of the bar to be heated, and the side contact members are shifted between their bar engaging and disengaging positions by means of a centrally arranged, common actuating device.

One practical embodiment of the invention is to be i described in detail in the following specification and it is illustrated in the accompanying drawings.

Fig. 1 is a longitudinal View of the improved contact device with certain parts shown in central vertical section and other parts shown in elevation. In this view, the contact device occupies a retracted position away from the end of the bar to be electrically contacted.

Fig. 2 is a view similar to Fig. 1 but with the contact device moved forward so as to cause an end contact member thereof to engage the end face of the bar.

Fig. 3 is a view similar to Fig. 2 but with the side contact members shifted radially inwardly to engage the side of the bar at a plurality of contact points.

Figs. 4-6 are also longitudinal views showing the contact device partly in section and partly in elevation and illustrating the manner in which the device may be shifted longitudinally so as toadapt it for use with bars of different lengths.

With reference now to the drawings and to Figs. 1-3 in particular, the improved contact device is seen to be comprised of at least two side contact members 1 symnietrically arranged about the axis xof the bar 2 to be ICC heated. In order to simplify the drawings, however, only one of the side contact members 1 and its supporting and actuating structure has been shown. The contact device also includes a front contact member 3 adapted to engage the end face of the bar 2 but this latter contact member may, in certain cases be deleted.

Each of the side contact members 1 is secured to a supporting arm 4. The rear end of arm 4 is pivotally connected at pin 5 and the front end of arm 4 is likewise pivotally connected to a hydraulic cylinder 6 by means of an angle lever 7. The latter is pivotally connected to the front end of arm 4 on a pin 8 which extends laterally outward therefrom, and is also pivotally connected through a pin and slot connection to an arm 9 which extends radially outwardly from the cylinder structure 6, the pin 10 being provided on arm 9 and the slot 11 being provided in the angle lever 7. n Also associated with the angle lever 7 is a spring 12 under compression, one end of this spring being connected to the angle lever 7 so as to always urge the latter in a counter clockwise direction of movement about the pin 10 so as to cause the outer end of arm 4 and side contact member 1 to move radially inwardly.

The cylinder 6 includes two piston elements thereon. One of these pistons 13 is connected to a piston rod 14 which extends through the right end of cylinder 6 and is secured rigidly to a contact bridge 15 which is carried by a tubular current supply member 16. A tlexible, copper strap 17 is secured at one end to the contact bridge 15 and at the other end to the supporting arm 4 so as to carry current through the arm to the side contact member 1 and also to the front contact member 3 via lever 7, arm 9 and cylinder 6, all of which are made from electrically conductive material.

The other piston 18 in cylinder 6 is seen to include two end portions 18a and an intermediate portion 18b which is tapered. Engaged with this tapered portion are a plurality of pins 19 which are radially slidable in corresponding bores provided in the cylinder wall. The lower end of each pin 19 contacts the tapered piston face 18b and the upper end of each pin engages a cam surface 20 provided on the arm 4. Consequently, as piston 18 `is moved back and forth within cylinder 6, the pins 19 move radially inward and outward.

Cylinder 6 also includes three ports for introducing and withdrawing the uid pressure medium. One of these ports 22 is located at the front end of the cylinder and serves to actuate piston 18 to the right as viewed in the drawing. Another port 23 is located at the center of the cylinder and serves to apply iiuid pressure against the inner ends of the pistons 13 and 18. The third port 24 is located at the rear of cylinder 6 and serves to apply fluid pressure against the outer side of piston 13.

A plurality of compression springs 2S are arranged horizontally within bores provided in a carrier member 26 located to the right of cylinder 6 which also carries the pivot pins 5 for the arms 4. The carrier member 26 is in turn mounted for limited horizontal movement upon and between the end anges 27a of a member 27 that is secured to the right end of cylinder 6. Piston rod 14 passes through the carrier member 26 and the flanged member 27, and the left ends of springs 2S which project outwardly from their bores are engaged with, and so as to bear against, the left flange of member 27 thus always to urge the latter and hence cylinder 6 and end contact member 3 to the left. v

Operation of the contact device is as follows:

Fig. 1 shows the contact device in its fully retracted position to the right and disengaged from the bar, the portion of cylinder 6 to the left of piston 18 being charged with the fluid pressure medium such as oil through the port 22. Ports 23, 24 are open, i. e. no Huid pressure is.

agresse applied to the cylinder through these ports. It will be seen from Fig. l, that with piston 18 moved to its extreme position to the right, pins 19 are forced to their outermost radial position thus causing the pivoted support member 4 to be pushed upwardly.

When now a bar to be heated is placed in the proper position for heating, for exampie, in accordance with the bar supporting arrangement shown in my co-pending application Serial No. 757,362, led August 26, 1958, fluid pressure is applied to the cylinder 6 through the center port 23. Since piston 13 is. immovable and piston 18 also cannot move because of the lluid pressure at the opposite side thereof, the entire contact device will be displaced to the left and come to the position shown in Fig. 2, wherein the end contact member 3 engages the end face of bar 2. At this time, the side contact members 1 are still in their raised position. In order to now bring the side contacts radially inward so as to engage the side of bar 2, port 22 is relieved of fluid pressure, i. e. the fluid in this part of cylinder 6 is no longer under pressure and can be forced out by movement of piston 18. Thus the duid pressure prevailing at the right side of piston 13 causes the latter to be displaced leftward to the position shown in Fig. 3 and eject through port 22 the fluid medium from this portion of the cylinder. As piston 18 moves to the left, the downwardly inclined intermediate portion 13b perm-its the pins 19 to move radially inward and releases the several arms d for radial inward movement under the action of the springs 12 which, as previously explained, constantly urge the arms 4 to their radially inward position. The front contact 3 is urged to the left against the end face of bar 2 by the springs 25.

All of the cylinder ports 22, 23 and 2d are now relieved from pressure in which event neither of pistons 13 and 18 will be subjected to tlui-d pressure and hence the entire contact pressure will be produced by the forces of springs 12 and 25.

It will be understood that a contact device as has been described will also be located at the other end of the bar and connected to another current supply tube similar to current supply tube 16, the two tubes being connected respectively to the terminals of an electrical power supply in order to send a current longitudinally through the bar.

When the bar has been heated electrically and annealed and is then ready to be removed for replacement by the next bar to be heated, pressure lluid is applied through port 22 causing piston 18 to shift to the right thus causing pins 19 to move radially outward and force the arms Li and side contact members 1 also radially outward so as to release them from the bar. At the same time there will be a slight displacement of the arms i and their common carrier member 26 to the left thus causing springs 25 to be further compressed. Pressure fluid is then introduced to cylinder 6 through port 24 thus causing the entire contact assembly to shift to the right to the initial or starting position shown in Fig. l. y

It will be understood that various types of uid mediums may be used. ln addition to oil it is possible to use air or water as such pressure tluids. Moreover, it is possible to so design the apparatus that it operates on purely mechanical principles or upon electro-mechanical principles.

In the closed position of the contact devices, i. e. in the position shown in Fig. 3, they are free to move in an axial direction during the annealing operation so that no forces of any appreciable extent are transmitted to the bar. Any thermal expansion of the bar when heated is thus automatically absorbed by the contact devices. Due to the fact that the Contact members are only pressed upon the bar by compression springs, a certain centering of the bar is made possible by the contact device. Such centering has heretofore been impossible with contact devices wherein the pressure of each contact member is applied by a 'separate hydraulically operated piston.

Moreover, use of springs to attain the desired contact pressure has the great advantage that in the absence of uid pressure in the actuating cylinder, the heating and annealing process is not jeopardized by decreasing contact pressure.

1n ordery to enable the improved contact device to be l used for annealing treatment of bars of different lengths, the present invention includes means for adjustrng the positions of the Contact devices longitudinally of the axis on which the bar is supported. The adjustment feature is illustrated in Figs. 4-6 and it will be noted from these views that certain of the component parts such as the arms 4 and other side contact structure have been omitted in the interest of simplication of the drawing.

With reference now to Figs. 4 6, it will be seen that the carrier 26 is also provided with a double pawl 3i) that is engageable With a toothed rack 31, the pawl being actuated into and out of engagement with the rack teeth 31a by means of a lever 32. In a similar manner, the Contact bridge 15 is likewise provided with a double pawl 33 engageable with the toothed rack 31, the pawl 33 also being actuated by means of a lever 34 connected therewith.

In order to adjust the contact device to the left as viewed in Fig. 4, the contact bridge 15 is irst released by actuating lever 34 to the upright position thus releasing pawl 33 from the toothed rack 31, so that the contact device can be displaced longitudinally along the current supply tube 16. Fluid under pressure is now admitted into cylinder through port 24 thus causing piston 13, piston rod 14 and contact bridge 15 to be moved to the left, the cylinder 6, of course, remaining stationary` due to the engagement of pawl 30 with the toothed rack 31. This position is shown in Fig. 5. Lever 34 is then shifted back to its original position (I) shown in full lines so as to retain the contact bridge 15 in its new position. Lever 32 is now shifted to release pawl 30, port 24 is now placed in communication with the low pressure side of the iluid pressure supply system and fluid under pressure is then introduced into port 23. With piston 13 now xed in position because of its rigid connection with contact bridge 15 which is also now xed in its new position, introduction of pressure fluid through port 23 thus causes cylinder 6 and the various components attached thereto to be shifted to a new position to the left as shown in Fig. 6. Further shifting of cylinder 6 to the left can be obtained by repeating the procedure just described. If it is desired to adjust cylinder 6 to the right, the double pawls 30 and 33 are shifted in the opposite direction by moving levers 32 and 34 from position (l) to position ,(II).

1n conclusion it will be understood that while one practical embodiment of the invention has been described and illustrated, various modifications of the construction and arrangement of parts may be made without, however, departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

l. An electrical contact device for engaging the side of an elongated bar at the end thereof to be electrically heated comprising a plurality of contact members ar ranged about the bar axis,.means mounting said contact members for radial movement toward and away from said axis, spring means biasing said contact members radially inward to engage the side of the bar, and means common to all of said contact members for actuating the same in a radially outward direction against the counter force of said spring means.

.2. An electrical contact device for engaging the side of an elongated bar at the end thereof to be electrically heated comprising a plurality of contact members arranged about the bar axis, means mounting said contact members for radial movement toward and away from said axis, spring means biasing said contact members radially inward to engage the .side of the bar, said mounting means including a hydraulic cylinder arranged longitudinally of said bar axis, a piston in said cylinder and means actuated radially by displacement of said piston for actuating said contact members in a radially outward direction against the counter force of said spring means.

3. An electrical contact device for engaging the side of an elongated bar at the end thereof to be electrically heated comprising a plurality of contact members arranged about the bar axis, support means, an arm individual to and carrying each of said contact members pivotally mounted on said support means for movement thereof and also movement of said contact members in a radial direction toward and away from said bar axis, spring means biasing said arms and hence said contact members radially inward to engage the side of the bar, and means common to all said arms for actuating the same in a radially outward direction against the counter force of said spring means.

4. An electrical contact device for engaging the side of an elongated bar at the end thereof to be electrically heated comprising a plurality of contact members arranged about the bar axis, support means including a hy draulic cylinder arranged longitudinally along an extension of the bar axis, an arm individual to and carrying each of said contact members, said arms being pivotally mounted on said support means for movement thereof and also movement of said contact members in a radial direction toward and away from said bar axis, spring means biasing said arms and hence said contact members radially inward to engage the side of the bar, a piston in said cylinder and means actuated radially by displacement of said piston for actuating said arms in a radially outward direction against the counter force of said spring means.

5. An electrical contact device as dened in claim 4 wherein said piston has a tapered surface extending longitudinally of its direction of displacement, said tapered surface being engaged by said radially actuated arm actuating means.

6. An electrical contact device for engaging the side of an elongated bar at the end thereof to be electrically heated comprising a plurality of side contact members arranged about the bar axis, support means including a hydraulic cylinder arranged for displacement longitudinally along an extension of the bar axis, an electrically conductive arm individual to and carrying each of said contact members, said arms being pivotally mounted on said support means for movement thereof and also movement of said contact members in a radial direction toward and away from said bar axis, spring means biasing said arms and hence said contact members radially inward to engage the side of the bar, a rst piston in said cylinder, means actuated radially by displacement of said first piston for actuating said arms in a radially outward direction against the counter force of said spring means, a second piston in said cylinder, said second piston being fixed in position, and a port at each end of said cylinder and at the portion of said cylinder between said pistons for admitting and discharging pressure iiuid thereby to effect radial movement of said arms and longitudinal displacement of said cylinder in a direction toward and away from the bar end, and an end contact member carried at the end of said cylinder engaging the end face of said bar upon longitudinal displacement of said cylinder in the direction of the bar end.

7. An electrical contact device as dened in claim 6 and which further includes spring means cooperative with said hydraulic cylinder for biasing said hydraulic cylinder in the direction of said bar end.

8. An electrical contact device as defined in claim 6 wherein said second piston is secured to a stationary contact bridge electrically connected to one terminal of a source of electric power and which further includes conductive straps connecting said contact bridge With each of said arms.

9. An electrical Contact device as defined in claim 6 wherein said first piston has a tapered surface extending longitudinally of its direction of displacement, said tapered surface being engaged by said radially actuated arm actuating means, and wherein the outer ends of said arm actuating means engage inclined cam surfaces on said arms so as to also impart in addition to radial movement a slight longitudinal displacement of said cylinder in the direction of said bar end.

l0. An electrical contact device for engaging the side of an elongatedwbar at the end thereof to be electrically heated comprising a plurality of side contact members arranged about the bar axis, support means including a hydraulic cylinder arranged for longitudinal displacement along an extension of the bar axis, an electrically conductive arm individual to and carrying each of said side contact members, said arms being pivotally mounted on said support means for movement thereof and also movement of said contact members in a radial direction toward and away from said bar axis, spring means biasing said arms and hence said contact members radially inward to engage the side of the bar, a rst piston in said cylinder, means actuated radially by displacement of said rst piston for actuating said arms in a radially outward direction against the counter force of said spring means, Second piston in said cylinder, said second piston being secured to a contact bridge electrically connected to one terminal of a source of electric power, conductive strap means connecting said contact bridge with each of said arms, a port at each end of said cylinder and at the portion of said cyilnder between said lirst and second pistons for admitting and discharging pressure fluid thereby to elect radial movement of said arms and longitudinal displacement of said cylinder in a direction toward and away from the bar end, an end contact member carried by the end of said cylinder engaging the end face of said bar upon longitudinal displacement of said cylinder in the direction of the bar, a means for adjusting the position of said entire contact device along the bar axis to accommodate bars of different length comprising a toothed rack extending longitudinally of the bar axis, pawl means on said support means engageable with said rack and pawl means on said contact bridge engageable with said rack.

References Cited in the file of this patent UNITED STATES PATENTS 1,679,730 MacDonald et al. Aug. 7, 1928 

